P3D Re: Phantograms

[boris@xxxxxxxxxxxx (Boris Starosta)]

>From: Marcus Warrington <marcusw@xxxxxxxxx>
...
>Wow.. how did you shoot this and introduce the correct distortion factor.
>I ...>I assume that adjusting the film plane to be parallel with the floor
>
>while holding the lens at 45 degrees to the subject would introduce the correct
>distortion... or am I wrong ?

I think that might work, although you would have the problem (I think), of
the "far" part of the film receiving a reduced exposure.  Thus the model
would have to be lit with a perfectly controlled gradient of illumination,
very bright about the head, and rather dim towards the feet!

The difficult part in doing the phantogram was the distortion.  It has to
be a perfect perspective distortion, and cannot be done just using a 2-d
perspective tool, such as the one in photoshop.

I shot the model with my 35mm twin rig, in a very standard fashion.  I
scanned the slides (drum scanner) to a high resolution, and took the scans
into "3-d" software - Bryce.  There I used the scans as "gels" within light
sources that projected the image back down onto the "floor." This projected
image I rendered as the print. The geometry was very important, and I had
taken careful notes and measurements during the session.

In essence, I used the computer to reverse the flow of light, from the film
plane, back out through the lenses, past the 3-d image (the subject), and
onto the print.  The print thus became the "shadow" of my subject, with the
cameras functioning as lights.

I had to correct for the falloff in brightness in the distorted image that
occurred on the rendered print, because far away from the light, the image
was fainter.  That was easy, and I shall leave the solution as an exercise
for the student.

This description is obviously a bit simplified.  There were a number of
technical details that needed to be solved, with respect specifically to
the use of Bryce, registration of the two viewpoints, color control at the
print stage (my thanks to Ray Zone for invaluable advice!) etc.  Lots of
small fires to put out over the span of a week.

Anyway, I got the print two days ago, and it turned out GREAT.  The
illusion is even better than I imagined it would be.  It is a "windowless"
stereoscopic experience, about as close to virtual reality as I've seen (in
some ways much better than looking at a slide).  It really makes for an
ultimate anaglyph.

Boris



Boris Starosta            boris@xxxxxxxxxxxx
                          http://www.starosta.com
usa 804 979 3930          http://www.starosta.com/3dshowcase



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